Polyurethane and polyurethaneurea RIM elastomers require the use of tin catalysts for acceptable processing. In a system based on high molecular weight polyether polyols and aromatic diamine chain extenders, it is customary to use dibutyltin dilaurate to catalyze the hydroxyl-isocyanate (OH--NCO) reaction. Without this catalyst additive it is impossible to make a RIM part with sufficient green strength to be demolded. Yet, it is well known that the presence of tin catalyst in the final elastomer limits the thermal stability of the material since it can catalyze the unzipping of urethane bonds. The need for high thermal stability in RIM elastomers is the result of high paint baking temperatures. Physical distortion, cracking, oiling and blistering can be observed if tin catalyst is present to promote the chemical breakdown of urethane linkages.
One solution to this problem has been the use of polyurea RIM based on isocyanate-reactive components which do not contain OH group, e.g., aliphatic amine terminated polyethers as disclosed in U.S. Pat. No. 4,433,067. Since the reaction of the amino (--NH.sub.2) groups with NCO groups is so rapid, no tin catalyst is needed although there is still some benefit to their use in polyurea RIM elastomers as disclosed in U.S. Pat. No. 4,444,910. However, the drawback to this solution is the high reactivity of the aliphatic amine terminated polyethers which makes is difficult to achieve high modulus elastomers with good flowability. Additionally, these products are more expensive than conventional RIM polyols and are not available in "filled" versions such as polymer polyols, grafted polyols or PHD polyols.